Solution: Let a be any odd positive integer and b=4 By division Lemma there exist integer q and r such that
a = 4q + r , Where
⇒ a = 4q or ,a =4q+1 or , a = 4q +2 or , a =4q+3 ⇒ r = 0,1,2,3
⇒ a=4q+1 or , a= 4q +3
Hence any odd integer is of the form 4q+1 or , 4q +3
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